End-to-end multipathing through network having switching devices compatible with different protocols

ABSTRACT

A first cluster includes first switching devices that are compatible with a software-defined networking (SDN) protocol. A second cluster includes second switching devices within or partially overlapping the first cluster. Each second switching device is compatible with a protocol for an open systems interconnection (OSI) model layer. The first switching devices include one or more border switching devices located at a boundary between the first cluster and the second cluster. Each border switching device is also compatible with the protocol for the OSI model layer. The first switching devices effect first multipathing through the network except through the second cluster, and the second switching devices effect second multipathing just through the second cluster of the network. As such, the first switching devices and the second switching devices together effect end-to-end multipathing through both the first cluster and the second cluster of the network.

RELATED APPLICATIONS

The present patent application is related to the patent applicationentitled “multipath effectuation within singly contiguous network fabricvia switching device routing logic programming,” filed on Mar. 14, 2013,and assigned application Ser. No. 13/827,479.

BACKGROUND

Network fabrics include devices, which are often referred to as nodes,that are interconnected to one another through a web of variousswitching devices like routers, hubs, switches, and so on. The networkfabrics permit the devices to be interconnected for a variety ofdifferent purposes. For instance, the devices may be interconnected toimplement a local-area network or a wide-area network for datatransmission purposes, to implement a storage-area network, to achieveclustering, and so on.

SUMMARY

A method of an embodiment of the disclosure includes interfacing, at afirst port of a border switching device, a first cluster of firstswitching devices compatible with an SDN protocol. The method includesinterfacing, at a second port of the border switching device, a secondcluster of second switching devices compatible with a protocol for anOSI model layer. The method includes receiving, at the first port, datathrough the first cluster that is intended for a destination reachableonly through the second cluster. The data is formatted according to theSDN protocol. The method includes, in response to receiving the data atthe first port adding to the data, by the border switching device, aheader formatted according to the protocol for the OSI model layer. Themethod includes, also in response to receiving the data at the firstport, routing the data, including the header, from the second portthrough the second cluster to another border switching device that isclosest to the destination.

A method of another embodiment of the disclosure similarly includesinterfacing, at a first port of a border switching device, a firstcluster of first switching devices compatible with an SDN protocol. Themethod similarly includes interfacing, at a second port of the borderswitching device, a second cluster of second switching devicescompatible with a protocol for an OSI model layer. The method includesreceiving, at the second port, data through the second cluster that isintended for a destination reachable within the first cluster. The datais formatted according to the SDN protocol. The method includes, inresponse to receiving the data at the second port, removing a headerfrom the data, by the border switching device. The header is formattedaccording to the protocol for the OSI model layer. The method includes,also in response to receiving the data the first port, routing the data,without the header, from the first port through the first clustertowards the destination.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The drawings referenced herein form a part of the specification.Features shown in the drawing are meant as illustrative of only someembodiments of the invention, and not of all embodiments of theinvention, unless otherwise explicitly indicated, and implications tothe contrary are otherwise not to be made.

FIGS. 1A and 1B are diagrams of different examples of a heterogeneous orhybrid network.

FIG. 2 is a diagram of an example of a heterogeneous or hybrid networkthat shows rudimentary constituent switching devices thereof

FIG. 3 is a diagram of an example portion of a heterogeneous or hybridnetwork that shows how switching devices thereof can be programmed by anetwork fabric controller device.

FIGS. 4A, 4B, and 4C are flowcharts of example methods that togetherachieve end-to-end multipathing through a heterogeneous or hybridnetwork.

FIG. 5 is a diagram of another example of a heterogeneous or hybridnetwork that shows rudimentary constituent switching devices thereof.

DETAILED DESCRIPTION

In the following detailed description of exemplary embodiments of theinvention, reference is made to the accompanying drawings that form apart hereof, and in which is shown by way of illustration specificexemplary embodiments in which the invention may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention. Other embodiments may be utilized,and logical, mechanical, and other changes may be made without departingfrom the spirit or scope of the present invention. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the embodiment of the invention is defined only by theappended claims.

As noted in the background section, a network fabric includes devices,which can be referred to as nodes, that are interconnected to oneanother through a web of various switching devices like routers, hubs,switches, and so on. As such, the nodes can communicate with one anotherby transmitting data through the network fabric, and more specificallyvia the switching devices routing the data between the nodes. Differentswitching devices are compatible with different protocols.

For example, a traditional protocol that provides for communicationamong switching devices of a network fabric is a protocol for an opensystems interconnection (OSI) model layer, such as what is known as alayer-two protocol. Examples of layer-two protocols include thetransparent interconnection of lots of links (TRILL) layer-two protocol,and the shortest-path bridging (SPB) layer-two protocol. The TRILLlayer-two protocol is maintained by the Internet Engineering Task Force(IETF), which is an organized activity of the Internet Society (ISOC)based in Reston, Va. The SPB layer-two protocol is maintained as the802.11 aq standard by the Institute of Electrical and ElectronicsEngineers (IEEE) based in Washington, D.C.

More recently, software-defined networking (SDN) protocols have beenadopted. An SDN protocol differs in at least one respect from a moretraditional protocol in that the switching devices can be relatively lowcost and so-called “dumb” switching devices that do not have much if anybuilt-in routing logic. Instead, the switching devices are programmedand controlled by an external network fabric controller device over aprogramming path different than the data path and/or the control path ofthe network. An example of an SDN protocol is the OpenFlow protocolmaintained by the Open Networking Foundation of Palo Alto, Calif.

Many experts expect SDN protocols to ultimately supplant to at leastsome degree more traditional protocols, due to the extensibility,flexibility, and potential for cost savings that they provide. However,entities cannot be realistically expected to replace all their existingswitching devices with SDN protocol-compatible switching deviceswholesale at the same time, due to the expense of purchasing theequipment and the time and expense in setting up and configuring thesedevices. Therefore, for at least the foreseeable future, it is expectedthat heterogeneous or hybrid networks will become more prevalent if notthe norm, in which switching devices compatible with different protocolsare asked to coexist on the same network.

This scenario can be problematic, however, where multipathing isconcerned. Switching devices can and do fail, and a network fabric canbe susceptible to faults that prevent data from being successfullyrouted among the nodes. Therefore, it can be important to have multipleredundant paths through a network fabric, to ensure that data issuccessfully routed among nodes even in the presence of faults such asswitching device failure. One approach to achieving this is to providefor multipathing within a singly contiguous network fabric.

In a singly contiguous network fabric, there is just one physicallycontiguous network of switching devices. Multipathing ensures that thereare different paths between two given nodes through the network fabric.The multipaths themselves can be disjoint or shared. Shared multipathshave one or more switching devices in common, but still vary from oneanother. Disjoint multipaths have no switching devices in common, bycomparison. Multipathing within heterogeneous or hybrid networks,however, is difficult; that is, it is difficult to guarantee that agiven multipath can span end-to-end across clusters of switching devicesthat are compatible with different networking communication protocols.

Techniques disclosed herein provide for innovative approaches torealizing multipathing within such a heterogeneous or hybrid network.These techniques are applicable in a network that includes at least twoclusters of switching devices. First switching devices of a firstcluster are compatible with an SDN protocol, whereas second switchingdevices of a second cluster within or partially overlapping the firstcluster are compatible with a protocol for an OSI model layer. The firstswitching devices include border switching devices located at a boundarybetween the two clusters. Each border switching device is compatiblewith the protocol for the OSI model layer in addition to beingcompatible with the SDN protocol.

The first switching devices effect multipathing through the networkexcept through the second cluster, whereas the second switching deviceseffect second multipathing just through the second cluster. As such, thefirst and second switching devices, including the border switchingdevices, together effect end-to-end multipathing through both the firstand second clusters of the network. To the first cluster, the secondcluster may be effectively treated as a black box, such as a singleswitching device, even though the second cluster is in fact made up ofmultiple switching devices.

In this respect, in one implementation the SDN protocol of the firstcluster may be the OpenFlow protocol, whereas the OSI model layerprotocol of the second cluster may be the TRILL or the SBP protocol. Theborder switching devices are compatible with both protocols, and haveports to connect to both clusters. When data from the first cluster hasto traverse the second cluster to reach its destination, the borderswitching devices add and remove headers to the data as appropriate toensure that the data can travel through the second cluster. The firstswitching devices assume responsibility for multipathing within thefirst cluster, whereas the second switching devices assumeresponsibility for multipathing within the second cluster, to ensureend-to-end multipathing through the network as a whole.

FIGS. 1A and 1B show different examples of a heterogeneous or hybridnetwork 100. The network 100 includes a first cluster 102 and a secondcluster 104. In the example of FIG. 1A, the second cluster 104 iscompletely within the first cluster 102. In the example of FIG. 1B, thesecond cluster 104 at least partially overlaps the first cluster 102.The first cluster 102 is compatible with an SDN protocol, such as theOpenFlow protocol, whereas the second cluster 104 is compatible with aprotocol for an OSI model layer, such as the TRILL or the SPB layer-twoprotocol.

End-to-end multipathing is effected through the heterogeneous or hybridnetwork 100 as a whole. This means that there are multiple paths throughthe network 100 as a whole. End-to-end multipathing in the context ofthe network 100 further means that there can be first multipathingwithin and provided by the first cluster 102, and second multipathingwithin and provided by the second cluster 104. The multipathing providedby the first and second clusters 102 and 104 thus effect the end-to-endmultipathing through the network 100 as a whole.

For example, in FIG. 1A, data may have to be transmitted from a point106 at one edge of the first cluster 102 to a point 108 at another edgeof the first cluster 102, which may require transmission of the datathrough the second cluster 104 from a point 110 at one edge thereof to apoint 112 at another edge thereof. Therefore, multipaths 114 between thepoints 106 and 110 through the first cluster 102 are determined, as aremultipaths 116 between the points 110 and 112 through the second cluster104 and multipaths 118 between the points 112 and 108 through the firstcluster 102. The multipaths 114 and 118 make up the first multipathingeffected within and provided by the first cluster 102, whereas themultipaths 116 make up the second multipathing effect within andprovided by the second cluster 104, to achieve end-to-end multipathingthrough the heterogeneous or hybrid network 100 as a whole.

As another example, in FIG. 1B, data may have to be transmitted from apoint 120 at an edge of the first cluster 102 to a point 122 at an edgeof the second cluster 104. Therefore, multipaths 126 through the firstcluster 102 between the point 120 at the edge of the first cluster 102and a point 124 at a boundary between the first and second clusters 102and 104 are determined, as are multipaths 128 through the second cluster104 between the points 124 and 122. The multipaths 126 make up the firstmultipathing effected within and provided by the first cluster 102,whereas the multipaths 128 make up the second multipathing effectedwithin and provided by the second cluster 104, to achieve end-to-endmultipathing through the heterogeneous or hybrid network 100 as a whole.

FIG. 2 shows a rudimentary example implementation of the heterogeneousor hybrid network 100 of the example of FIG. 1. The first cluster 102includes first switching devices 202A, 202B, 202C, 202D, and 202E,collectively referred to as the first switching devices 202. The firstswitching devices 202 are compatible with an SDN protocol, like theOpenFlow protocol, and are located within or at an edge of the firstcluster 102 other than a boundary between the first cluster 102 and thesecond cluster 104.

The second cluster 104 includes second switching devices 204A and 204B,collectively referred to as the second switching devices 204. The secondswitching devices 204 are compatible with a protocol for an OSI modellayer, such as the TRILL layer-two protocol or the SBP layer-twoprotocol. The second switching devices 204 are located within or at anedge of the second cluster 104 other than a boundary between the firstcluster 102 and the second cluster 104.

The heterogeneous or hybrid network 100 also includes border switchingdevices 206A and 206B, collectively referred to as the border switchingdevices 206. The border switching devices 206 are located at a boundarybetween the first cluster 102 and the second cluster 104. The borderswitching devices 206 are compatible with both the SDN protocol and theprotocol for an OSI model layer. In this sense, the border switchingdevices 206 can be considered as first switching devices of the firstcluster 102, as well as second switching devices of the second cluster104.

The switching devices 202, 204, and 206 are switching devices likerouters, hubs, switches, and so on. There are at least one or more firstswitching devices 202, one or more second switching devices 204, and oneor more border switching devices 206. The switching devices 202, 204,and 206 include ports 208A, 208B, 208C, 208D, 208E, 208F, 208I, 208J,208K, 208L, 208M, 208N, 208O, 208P, 208Q, 208R, 208S, and 208T,collectively referred to as the ports 208. The ports 208 interconnectthe switching devices 202, 204, and 206. Other ports, not depicted inFIG. 2, can connect the switching devices 202, 204, and 206 to othertypes of devices, or nodes.

Each port 208 is a network port that is compatible with the SDN protocolor the protocol for the OSI model layer. The ports 208 of the firstswitching devices 202 are compatible with the SDN protocol, and theports 208 of the second switching devices 204 are compatible with theprotocol for the OSI model layer. Each ports 208 of each borderswitching device 206 can be programmed to be compatible with the SDNprotocol or with the protocol for the OSI model layer, but not bothprotocols at the same time.

The ports 208A, 208B, 208C, 208D, 208E, 208F, 208I, 208J, 208K, and 208Lare compatible with the SDN protocol. The port 208A of the firstswitching device 202A is connected to the port 208B of the firstswitching device 202B, and the port 208C of the first switching device202A is connected to the port 208D of the border switching device 206A.The port 208E of the first switching device 202B is connected to theport 208F of the first switching device 202C. The port 208I of the firstswitching device 202D is connected to the port 208J of the borderswitching device 206B. The port 208K of the first switching device 202Dis connected to the port 208L of the first switching device 202E.

The ports 208M, 208N, 208O, 208P, 208Q, 208R, 208S, and 208T arecompatible with the protocol for the OSI model layer. The port 208M ofthe border switching device 206B is connected to the port 208N of thesecond switching device 204A. The port 208O of the border switchingdevice 206B is connected to the port 208P of the second switching device204B. The port 208Q of the second switching device 204A is connected tothe port 208R of the border switching device 206A. The port 208S of theborder switching device 206A is connected to the port 208T of the secondswitching device 204B.

Multipathing within the first cluster 102, via the first switchingdevices 202 and the border switching devices 208, can be effected bysuitably programming the switching devices 202 and 208. For example, inthe context of the OpenFlow protocol, multipathing can be achieved asdescribed in the patent application entitled “multipath effectuationwithin singly contiguous network fabric via switching device routinglogic programming” noted above. Multipathing can be effected within thefirst cluster 102 in other ways as well.

Multipathing within the second cluster 104, via the second switchingdevices 204 and the border switching devices 206, can be effected asprovided by the TRILL layer-two protocol or the SPB layer-two protocol,and by suitably programming the border switching devices 206, withoutnecessarily having to program the second switching devices 204. Forexample, a type-length-value (TLV) extension can be provided for theTRILL layer-two protocol to achieve such multipathing within the secondcluster 104. The border switching devices 206 in particular can use theextension to cause multipathing through the second cluster 104. The TLVextension can be used to force unicast traffic through the secondcluster 104 to follow disjoint or shared multipaths.

End-to-end multipathing through the heterogeneous or hybrid network 100means that it is guaranteed data can take shared or disjoint multipathsthrough the network 100. For at least some data, this means that boththe first cluster 102 and the second cluster 104 have to be traversed,whereas for other data, just the first cluster 102 may have to betraversed. As an example of the latter, if data is received at the firstswitching device 202A that is intended for the first switching device202C, the first switching device 202A can transmit this data through thefirst switching device 202B to reach the first switching device 202C,completely within the first cluster 102 and without having to traversethe second cluster 104.

However, as an example of the former, if data is received at the firstswitching device 202A that is intended for the first switching device202D, the data has to be transmitted through the second cluster 104 toreach first switching device 202D. In the example of FIG. 2, there is noway for the first switching device 202A to communicate with the firstswitching device 202D except through the second cluster 104. Therefore,the first switching device 202A sends the data to the border switchingdevice 206A, which sends the data through the second switching device204A or 204B to the border switching device 206B, which sends the datato the first switching device 202D.

Each border switching device 206 is aware of every other borderswitching device 206 so that the border switching devices 206 canproperly transmit data through the second cluster 104. In the example ofFIG. 2, this means that the border switching device 206A is aware of theborder switching device 206B, and vice-versa. Each border switchingdevice 206 receives and sends data within the first cluster 102 via aport 208 thereof that is specifically compatible with the SDN protocol,and that interfaces the border switching device 206 in question to oneof the first switching devices 202. Each border switching devices 206similarly receives and sends data within the second cluster 104 via aport 208 thereof that is specifically compatible with the protocol forthe OSI model layer, and that interfaces the border switching device 206in question to one of the second switching devices 204.

Note in this respect that in the example of FIG. 2, each borderswitching device 206 is depicted as including one SDNprotocol-compatible port 208 and two OSI model layer protocol-compatibleports 208. More generally, however, each border switching device 206includes at least one SDN protocol-compatible port 208 and at least oneOSI model layer protocol-compatible port 208. Similarly, more generallyeach first switching device 202 includes at least one SDNprotocol-compatible port 208, and more generally each second switchingdevice 204 includes at least one OSI model layer protocol-compatibleport 208.

FIG. 3 shows an example portion of the network 100, specifically justthe first cluster 102 thereof, to depict how the first switching devices202 and/or the border switching devices 206 can be programmed to effectmultipathing within the first cluster 102, and how the border switchingdevices 206 can be programmed to effect multipathing within the secondcluster 104. Note that the second cluster 104 is not depicted in FIG. 3for illustrative clarity. There is a network fabric controller device302, which can be an OpenFlow controller (OFC) device, and in theexample described herein, is presumed to be such. The OpenFlow protocolpermits an OpenFlow switch, or switching device, like the switchingdevices 202 and 206, to be completely programmed by an OFC device. AnOFC device thus can program OpenFlow switching devices to perform datarouting as desired.

The network fabric controller device 302 includes network managing logic304 and network connecting hardware 306. The controller device 302 canalso include other components, in addition to the network connectinghardware 306 and/or the network managing logic 304. The networkconnecting hardware 306 is hardware that connects the controller device302 to the first switching devices 202 and the border switching devices206 via a programming path or channel 308.

The network managing logic 304 may be implemented as software, hardware,or a combination of software and hardware. As one example, the networkmanaging logic 304 may be a computer program stored on acomputer-readable data storage medium and executable by a processor. Asanother example, the network managing logic 304 may be implemented ashardware, such as an application-specific integrated circuit (ASIC), afield-programmable gate array (FPGA), and so on.

The network managing logic 304 performs the programming of the switchingdevices 202 and 206 to effect end-to-end multipathing through thenetwork 100 as has been described. That is, the first switching devices202 and/or the border switching devices 206 are programmed over theprogramming path or channel 308 to effect first multipathing within thefirst cluster 102, and the border switching devices 206 are programmedover this same path or channel 308 to effect second multipathing withinthe second cluster 104. Because multipathing is achieved in each of thefirst and second clusters 102 and 104, this means that end-to-endmultipathing over the network 100 as a whole is effected.

The programming path or channel 308 is the path or channel of thenetwork fabric of the first cluster 102 by which components thereof,such as the switching devices 202 and 206, are programmed. For instance,the network fabric controller device 302 can load routing tables and/orother types of programming logic into the switching devices 202 and 206.As such, the controller device 302 can effectively control how theswitching devices 202 and 206 route the data through the first cluster102 (and in the case of the border switching devices 206, through thesecond cluster 104).

By comparison, the first switching devices 202 and the border switchingdevices 206 are intraconnected and interconnected via a data path orchannel 310. The data path or channel 310 is thus the path or channel ofthe network fabric of the first cluster 102 by which components thereof,such as the switching devices 202 and 206, communicate data. The networkfabric controller device 302 is not typically connected to the data pathor channel 310.

A third channel may also be presented, but which is not depicted in FIG.3, and which is referred to as a control path or channel, along whichcontrol information regarding such components of the network fabric ofthe first cluster 102 is transmitted. This control information caninclude port information, address information, and other types ofcontrol information regarding these components. The network fabriccontroller device 302 may not typically be connected to the control pathor channel, but rather a device that is referred to as a fiber channel(FC) or FC over Ethernet (FCoE) channel forwarder (FCF) device is, andwhich may be communicatively connected to the controller device 302. Inone implementation, however, a single device, such as a single servercomputing device, may include the functionality of such an FCF deviceand the functionality of the controller device 302. Like the controllerdevice 302, an FCF device does not route the actual data through thenetwork fabric itself

The various paths or channels may be logical/virtual or physicallydiscrete paths or channels. For example, there may indeed be just singlehardware lines interconnecting the ports 208 of the switching devices202 and 206 and ports of the network fabric controller device 302.However, these hardware lines may have the paths or channels virtuallyor logically overlaid thereon or defined therein. For instance, theprogramming path or channel 308 may be a secure socket layer (SSL)channel that uses the same hardware lines that the data path or channel310 uses.

FIGS. 4A, 4B, and 4C show example methods 400, 410, and 420,respectively, but which may be part of the same method in someimplementations. The methods 400, 410, and 420 can be implemented as oneor more computer programs stored on a computer-readable data storagemedium. Execution of the computer programs, such as by a processor of adevice, causes the method(s) in question to be performed.

In the method 400 of FIG. 4A, a first port 208 of a border switchingdevice 206 is interfaced to the first cluster 102 of the first switchingdevices 202 that are compatible with an SDN protocol (402). As such, theborder switching device 206 sends and receives SDN protocol-formatteddata using this first port 208. Similarly, a second port 208 of theborder switching device 206 is interfaced to the second cluster 104 ofthe second switching devices 204 that are compatible with an OSI modellayer protocol (404). As such, the border switching device 206 sends andreceives OSI model layer protocol-formatted data using this second port208.

End-to-end multipathing is then suitably achieved (406), by each borderswitching device 206 in concert with the first switching devices 202 andthe second switching devices 204. As noted above, the end-to-endmultipathing is through both the first and second clusters 102 and 104.That is, this multipathing includes (first) multipathing through thefirst cluster 102, via the border switching devices 206 in concert withthe first switching devices 202, as well as (second) multipathingthrough the second cluster 104, via the border switching devices 206 inconcert with the second switching devices 204.

The method 410 of FIG. 4B and the method 420 of FIG. 4C are described inrelation to the example presented above in relation to FIG. 2. In thisexample, the border switching device 206A receives data through thefirst cluster 102 from the first switching device 202A intended for thefirst switching device 202D. The border switching device 206A sends thedata through the second cluster 104 to the border switching device 206B.The border switching device 206B then sends the data through the firstcluster 102 to the first switching device 202D.

In the method 410 of FIG. 4B, then, the border switching device 206Areceives at the port 208D data through the first cluster 102 that isintended for a destination—the first switching device 202D—that isreachable only through the second cluster 104 (412). The data isformatted according to the SDN protocol of the first cluster 102,insofar as the data was received over the first cluster 102. In responseto receiving this data at the port 208D, the border switching device206A performs the following.

First, the border switching device 206A adds a header to the data (414).The header is formatted according to the OSI model layer protocol. Byadding such a header to the SDN protocol-formatted data, the data cannow be sent through the second cluster 104 using the OSI model layerprotocol. Therefore, second, the border switching device 206A routes thedata, including the header, from the port 208R or 208S through thesecond cluster 104 to the border switching device 206B (416), which isthe closer or closest border switching device 206 to the destination ofthe data, the first switching device 202D.

In the method 420 of FIG. 4C, the border switching device 206B receivesat the port 208M or 208O this data through the second cluster 104 thatis intended for a destination, the first switching device 202D, withinthe first cluster 102 (422). The data as received by the borderswitching device 206B includes the header that the border switchingdevice 206A added thereto in part 414. In response to receiving thisdata at the port 208M or 208O, the border switching device 206B performsthe following.

First, the border switching device 206B removes or strips the headerfrom the data (424). By removing the OSI model layer protocol-formattedheader from the data, the data can now be sent through the first cluster102 using the SDN protocol. Therefore, second, the border switchingdevice 206B routes the data, without the header, from the port 208Jthrough the first cluster 102 to or towards the destination of the data(426), which is the first switching device 202D.

It is noted that in some networking topologies, the first cluster 102may include one or more switching devices that do not support and thusare not compatible with the SDN protocol. Where there is a limitednumber of such switching devices, it may not be advisable to add borderswitching devices around them to create another contained cluster, likethe second cluster 104, within the first cluster 102. This is becausedoing so can add unneeded complexity to the resulting network 100.Rather, a different approach can be employed, as is now described.

FIG. 5 shows a version of the example heterogeneous or hybrid network100 of FIG. 2, in which there is such a third switching device 502 thatdoes not support and is not compatible with the SDN protocol. In FIG. 5,the ports 208 of the switching devices 202, 204, and 206 (and ports ofthe switching device 502) are not depicted for illustrative clarity andconvenience. The third switching device 502 is connected to the firstswitching device 202A and to the first switching device 202E.

It is presumed that the first switching device 202A is to send data tothe first switching device 202E. Although there is a path through thenetwork 100 that avoids having to route data through the third switchingdevice 502—namely, the path including the border switching devices 206,the second cluster 104, and the first switching device 202D—this path isnot as desirable as routing the data through the third switching device502. This is because the data may take longer to reach the firstswitching device 202E, because the number of hops—i.e., the number ofswitching devices that the data has to traverse—is longer if the datawere routed through the second cluster 104.

Therefore, the first switching devices 202A and 202E can effectmultipathing through the third switching device 502 by tunneling the SDNprotocol-formatted traffic through the third switching device 502. Thetunneling can be achieved by using encapsulation at a networkingprotocol layer level higher than the layer level of the SDN protocol.For example, if the SDN protocol is a layer-two protocol, the dataformatted according to the SDN protocol can be encapsulated at alayer-three protocol, such as the Internet Protocol (IP). This approachthus is another technique by which end-to-end multipathing through aheterogeneous or hybrid network 100 can be achieved.

It is noted that, as can be appreciated by one those of ordinary skillwithin the art, aspects of the present invention may be embodied as asystem, method or computer program product. Accordingly, aspects of theembodiments of the invention may take the form of an entirely hardwareembodiment, an entirely software embodiment (including firmware,resident software, micro-code, etc.) or an embodiment combining softwareand hardware aspects that may all generally be referred to herein as a“circuit,” “module” or “system.” Furthermore, aspects of the presentinvention may take the form of a computer program product embodied inone or more computer readable medium(s) having computer readable programcode embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium include the following: an electrical connection havingone or more wires, a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), an optical fiber, a portablecompact disc read-only memory (CD-ROM), an optical storage device, amagnetic storage device, or any suitable combination of the foregoing.In the context of this document, a computer readable storage medium maybe any tangible medium that can contain, or store a program for use byor in connection with an instruction execution system, apparatus, ordevice.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device. Program codeembodied on a computer readable medium may be transmitted using anyappropriate medium, including but not limited to wireless, wireline,optical fiber cable, RF, etc., or any suitable combination of theforegoing.

In general, a computer program product includes a computer-readablemedium on which one or more computer programs are stored. Execution ofthe computer programs from the computer-readable medium by one or moreprocessors of one or more hardware devices causes a method to beperformed. For instance, the method that is to be performed may be oneor more of the methods that have been described above.

The computer programs themselves include computer program code. Computerprogram code for carrying out operations for aspects of the presentinvention may be written in any combination of one or more programminglanguages, including an object oriented programming language such asJava, Smalltalk, C++ or the like and conventional procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The program code may execute entirely on the user's computer,partly on the user's computer, as a stand-alone software package, partlyon the user's computer and partly on a remote computer or entirely onthe remote computer or server. In the latter scenario, the remotecomputer may be connected to the user's computer through any type ofnetwork, including a local area network (LAN) or a wide area network(WAN), or the connection may be made to an external computer (forexample, through the Internet using an Internet Service Provider).

Aspects of the present invention have been described above withreference to flowchart illustrations and/or block diagrams of methods,apparatus (systems) and computer program products according toembodiments of the invention. It will be understood that each block ofthe flowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

It is finally noted that, although specific embodiments have beenillustrated and described herein, it will be appreciated by those ofordinary skill in the art that any arrangement calculated to achieve thesame purpose may be substituted for the specific embodiments shown. Thisapplication is thus intended to cover any adaptations or variations ofembodiments of the present invention. As such and therefore, it ismanifestly intended that this invention be limited only by the claimsand equivalents thereof

We claim:
 1. A method comprising: interfacing, at a first port of aborder switching device, a first cluster of first switching devicescompatible with a software-defined networking (SDN) protocol;interfacing, at a second port of the border switching device, a secondcluster of second switching devices compatible with a protocol for anopen systems interconnection (OSI) model layer; receiving, at the firstport, data through the first cluster that is intended for a destinationreachable only through the second cluster, the data formatted accordingto the SDN protocol; in response to receiving the data at the firstport, adding to the data, by the border switching device, a headerformatted according to the protocol for the OSI model layer; and routingthe data, including the header, from the second port through the secondcluster to another border switching device that is closest to thedestination.
 2. The method of claim 1, further comprising effectingend-to-end multipathing, by the border switching device in concert withthe second switching devices and with other of the first switchingdevices, through both the first cluster and the second cluster,including first multipathing through the first cluster by the borderswitching device in concert with the other of the first switchingdevices and second multipathing through the second cluster by the borderswitching device in concert with the second switching devices.
 3. Amethod comprising: interfacing, at a first port of a border switchingdevice, a first cluster of first switching devices compatible with asoftware-defined networking (SDN) protocol; interfacing, at a secondport of the border switching device, a second cluster of secondswitching devices compatible with a protocol for an open systemsinterconnection (OSI) model layer; receiving, at the second port, datathrough the second cluster that is intended for a destination reachablewithin the first cluster, the data formatted according to the SDNprotocol; in response to receiving the data at the second port, removinga header from the data, by the border switching device, the headerformatted according to the protocol for the OSI model layer; and routingthe data, without the header, from the first port through the firstcluster towards the destination.
 4. The method of claim 3, furthercomprising effecting end-to-end multipathing, by the border switchingdevice in concert with the second switching devices and with other ofthe first switching devices, through both the first cluster and thesecond cluster, including first multipathing through the first clusterby the border switching device in concert with the other of the firstswitching devices and second multipathing through the second cluster bythe border switching device in concert with the second switchingdevices.